[Positron emission tomography and single photon CT in the diagnosis of cerebrovascular disorders]

The positron emission tomography (PET) and single photon emission CT (SPECT) revealed the pathophysiology of ischemic brain in the transaxial images. There are several limitations in PET studies by continuous inhalation method using oxygen-15 labeled gases. There has been a suspicion about the constancy between the red cell volume and plasma volume in the ischemic brain. We measured plasma volume by PET using Cu-62 labeled human serum albumin in cases of internal carotid artery occlusion. There was no remarkable plasma volume alterations between the ischemic and non-ischemic hemisphere. Powers et al demonstrated the relationships between the intracranial perfusion pressure changes and vascular or metabolic adaptations. The important issue in acute stage of stroke is to differentiate the truly alive and completely destroyed tissue. Cerebral blood flow change might be affected during acute stage by diaschisis. Recent examination using benzodiazepine receptor imaging by SPECT might have a potential to depict the damaged tissues, because cortical neuronal cell bodies have a lot of the receptors and an ischemic insult induces the loss of the receptors. The relationship of crossed cerebellar hypoperfusion (CCH) and supratentorial circulatory conditions is attractive, because supratentorial hypometabolism of oxygen induced more severe CCH in internal carotid artery occlusion. Therefore, we can predict the supratentorial oxygen metabolism by CCH in a case of internal artery occlusion. We have a lots of tools to explore the pathophysiological states of ischemic brain. These must be dedicated to develop the more effective therapeutic procedures.